In radiosurgery or radiotherapy (collectively referred to as radiation treatment) very intense and precisely collimated doses of radiation are delivered to a target region in the body of a patient in order to treat or destroy lesions. Typically, the target region is composed of a volume of tumorous tissue. Radiation treatment requires an extremely accurate spatial localization of the targeted lesions. As a first step in performing radiation treatment, it is necessary to determine with great precision the location of a lesion and any surrounding critical structures, relative to the reference frame of the treatment device. Computed tomography (“CT”), magnetic resonance imaging (“MRI”) scans, and other diagnostic imaging modalities enable practitioners to precisely locate a lesion relative to skeletal landmarks or implanted fiducial markers. However, it is also necessary to control the position of the radiation source so that its beam can be precisely directed to the target tissue while avoiding adjacent critical body structures.
Thus, radiation treatment necessitates high precision diagnosis and high precision radiation source control. The consequences of deviating outside the prescribed tolerances for the diagnosis and the radiation source control can be potentially devastating to a patient. Accordingly, quality assurance mechanisms should be implemented to ensure proper alignment and configuration of the radiation delivery system prior to delivering a prescribed radiation dose to a patient.
Conventional quality assurance mechanisms include pointing the radiation source at a quality assurance (“QA”) marker, delivering a radiation dose to the QA marker, and then analyzing the QA marker itself to determine if the prescribed dose was actually delivered to the correct location. If the prescribed dose was delivered as expected, then the radiation treatment delivery system is deemed properly aligned. If the prescribed dose was not delivered as expected, then the radiation treatment delivery system is deemed misaligned.
Conventional QA markers include silver loaded gel capsules or photographic film inserts that can store readable information about the distribution of the radiation dose delivered to the QA marker. However, extracting this alignment information from silver loaded gels is a time consuming and costly task. Similarly, photographic film inserts are not easily inserted into or extracted from conventional QA markers, nor are the photographic film inserts easily aligned with the housing of the QA marker. As such, these conventional QA markers are time consuming and prone to human error.